U.S. patent application number 13/994414 was filed with the patent office on 2013-10-10 for closed-loop magnetic positioning of conveyor belts.
This patent application is currently assigned to LAITRAM, L.L.C.. The applicant listed for this patent is John F. Landrum, Glenn R. McCall. Invention is credited to John F. Landrum, Glenn R. McCall.
Application Number | 20130264175 13/994414 |
Document ID | / |
Family ID | 46314730 |
Filed Date | 2013-10-10 |
United States Patent
Application |
20130264175 |
Kind Code |
A1 |
Landrum; John F. ; et
al. |
October 10, 2013 |
CLOSED-LOOP MAGNETIC POSITIONING OF CONVEYOR BELTS
Abstract
A conveyor having a conveyor belt with magnetic properties that
allow the belt's position to be controlled by externally generated
magnetic fields and methods for controlling such a conveyor belt.
Sensors sense an operating condition of the belt, such as belt
speed, belt tension, belt loading, belt lateral, or radial,
position, or belt elevation, and send those measurements to a
controller. Electromagnets in the conveyor frame generate magnetic
fields that interact with the magnetic properties of the belt to
apply selected forces to position the belt in the conveyor. The
controller adjusts the strength and direction of the magnetic
fields generated by the electromagnets to control the operating
conditions of the belt.
Inventors: |
Landrum; John F.; (New
Orleans, LA) ; McCall; Glenn R.; (Harvey,
LA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Landrum; John F.
McCall; Glenn R. |
New Orleans
Harvey |
LA
LA |
US
US |
|
|
Assignee: |
LAITRAM, L.L.C.
Harahan
LA
|
Family ID: |
46314730 |
Appl. No.: |
13/994414 |
Filed: |
December 7, 2011 |
PCT Filed: |
December 7, 2011 |
PCT NO: |
PCT/US2011/063773 |
371 Date: |
June 14, 2013 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
61425620 |
Dec 21, 2010 |
|
|
|
Current U.S.
Class: |
198/617 ;
198/805 |
Current CPC
Class: |
B65G 43/02 20130101;
B65G 21/2009 20130101; B65G 15/02 20130101; B65G 15/64 20130101;
B65G 15/60 20130101 |
Class at
Publication: |
198/617 ;
198/805 |
International
Class: |
B65G 15/60 20060101
B65G015/60 |
Claims
1. A conveyor comprising: a conveyor frame; a conveyor belt
supported in the conveyor frame and having magnetic properties; a
plurality of electromagnets disposed along the conveyor frame and
arranged to generate magnetic fields attracting or repelling the
conveyor belt; a sensor sensing an operating condition of the
conveyor belt and providing a sensor signal representing the
operating condition; and a controller receiving the sensor signal
from the sensor and controlling the magnetic fields generated by
the electromagnets in response to the sensor signal to position the
conveyor belt in the conveyor frame.
2. A conveyor as in claim 1 wherein the conveyor belt includes a
plurality of magnets producing the magnetic properties of the
conveyor belt and arranged to interact with the magnetic fields
generated by the electromagnets.
3. A conveyor as in claim 2 wherein the magnets are disposed along
a first side edge of the conveyor belt and wherein the
electromagnets are disposed along the conveyor frame proximate the
first side edge of the conveyor belt.
4. A conveyor as in claim 2 wherein the conveyor belt includes
depending elements extending below the conveyor belt and housing
the magnets and wherein the electromagnets are disposed along the
conveyor frame proximate the depending elements.
5. A conveyor as in claim 1 wherein the conveyor belt is
magnetized.
6. A conveyor as in claim 1 wherein the conveyor belt is
unmagnetized.
7. A conveyor as in claim 1 wherein the conveyor frame includes a
turn and wherein the conveyor belt includes magnets in a side edge
at the inside of the turn and wherein the electromagnets are
disposed along the conveyor frame at the inside of the turn to
repel the magnets in the side edge of the conveyor belt.
8. A conveyor as in claim 1 wherein the sensor rides with the
conveyor belt.
9. A conveyor as in claim 1 wherein the sensor is mounted in the
conveyor frame.
10. A conveyor as in claim 1 wherein the sensor senses belt speed,
belt tension, belt loading, belt lateral position, or belt
elevation in the conveyor frame.
11. A conveyor as in claim 1 comprising a motor driving the belt
and wherein the sensor is a current sensor sensing motor
current.
12. A conveyor as in claim 1 wherein the electromagnets are
positioned along the conveyor frame to repel the conveyor belt from
below.
13. A conveyor as in claim 1 wherein the electromagnets are
positioned along the conveyor frame to attract the conveyor belt
from above.
14. A conveyor as in claim 1 wherein the electromagnets are
positioned along one side of the conveyor frame to repel the
conveyor belt away from the side of the conveyor frame.
15. A conveyor as in claim 1 wherein the controller controls the
strength of the magnetic fields generated by the electromagnets as
a function of the sensed operating condition.
16. A method for controlling a conveyor belt, comprising: advancing
a conveyor belt having a magnetic property along a conveying path;
sensing an operating condition of the conveyor belt; subjecting the
conveyor belt to magnetic fields along the conveying path;
adjusting the strength of the magnetic fields as a function of the
sensed operating condition to position the conveyor belt laterally
or vertically along the conveying path.
17. The method of claim 16 wherein subjecting the conveyor belt to
magnetic fields along the conveyor comprises repelling the conveyor
belt.
18. The method of claim 16 wherein subjecting the conveyor belt to
magnetic fields along the conveyor comprises attracting the
conveyor belt.
19. The method of claim 16 wherein adjusting the strength of the
magnetic fields comprises adjusting the current in electromagnets
disposed along the conveying path.
20. The method of claim 16 wherein the operating condition is belt
speed, belt tension, belt loading, belt lateral position, belt
elevation, or belt motor current.
Description
BACKGROUND
[0001] The invention relates generally to power-driven conveyors
and more particularly to belt conveyors and associated methods in
which conveyor belts having magnetic properties are repelled or are
attracted by controllable electromagnets to control belt position
to reduce friction or otherwise improve conveyor performance.
[0002] Permanent magnets have been used in belt and chain conveyors
to reduce friction between belts and conveyor frames and to
levitate belts by the force of magnetic repulsion and to prevent
belts from rising out of their tracks by the force of magnetic
attraction. Permanent magnets in a conveyor frame form magnetic
fields that interact with permanent magnets or metallic materials
in a conveyor belt to apply forces on the belt that can, for
example, be directed to reduce the frictional contact between the
belt and the conveyor frame. The strength and arrangement of the
magnets is selected for the specific application. Often, however,
conveyor operating conditions, such as belt load and belt speed,
can change. The change in operating conditions may change the belt
dynamics enough that the strength and arrangement of the permanent
magnets are suboptimal for the changed operating condition.
SUMMARY
[0003] A conveyor embodying features of the invention comprises a
conveyor belt supported in a conveyor frame. The conveyor belt has
magnetic properties that allow the belt to be attracted or repelled
by a magnetic field. Electromagnets disposed along a conveyor frame
are arranged to generate magnetic fields that attract or repel the
conveyor belt. A sensor sensing an operating condition of the
conveyor belt provides a sensor signal that represents the
operating condition. A controller receives the sensor signal and
controls the electric fields generated by the electromagnets in
response to the signal to position the conveyor belt in the
conveyor frame.
[0004] In another aspect of the invention, a method for controlling
a conveyor belt comprises: (a) advancing a conveyor belt having
magnetic properties along a conveying path; (b) sensing an
operating condition of the conveyor belt; (c) subjecting the
conveyor belt to magnetic fields along the conveying path; and (d)
adjusting the strength of the magnetic fields as a function of the
sensed operating condition to position the conveyor belt laterally
or vertically along the conveying path.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] These features and aspects of the invention, as well as its
advantages, are further described in the following description,
appended claims, and accompanying drawings, in which:
[0006] FIG. 1 is a top plan view of a portion of a turn segment of
a conveyor embodying features of the invention including a radius
conveyor belt with magnets in the inner belt edge and an inner rail
with electromagnets;
[0007] FIG. 2 is an oblique perspective view of the conveyor of
FIG. 1;
[0008] FIG. 3 is an oblique perspective view of a conveyor having
an electromagnet repelling a magnet in the outer edge of a belt at
the outside of a turn;
[0009] FIGS. 4A-4D are isometric, top plan, cross sectional, and
enlarged views of a conveyor having an electromagnet attracting
magnetic materials in a belt at the outside of a turn, and FIG. 4E
is a bottom plan view of an edge module of the belt;
[0010] FIG. 5 is an oblique perspective view of a conveyor having
an electromagnet repelling a hold down on a belt to hold the belt
down at the bottom side of a radius conveyor belt in the outside of
a turn;
[0011] FIGS. 6A-6C are isometric, cross sectional, and enlarged
views of a levitating conveyor embodying features of the invention,
including repelling electromagnets above and below the belt
carryway, and FIG. 6D is a bottom plan view of an edge module of
the belt; and
[0012] FIG. 7 is a block diagram of a control system usable with
the conveyors of FIGS. 1-6.
DETAILED DESCRIPTION
[0013] A portion of one version of a conveyor embodying features of
the invention is shown in FIGS. 1 and 2. The conveyor 10 includes a
conveyor belt 12 advancing in a direction of belt travel 14 in a
turn 15. The exemplary belt 12 shown in FIG. 1 is a modular plastic
conveyor belt capable of side flexing to negotiate turns. One
example of such a belt structure is the INTRALOX.RTM. Series 2200
Radius Flush Grid belt manufactured and sold by Intralox, L.L.C. of
Harahan, La., U.S.A. The endless belt comprises a series of rows 16
of belt modules 18 linked together at hinge joints by hinge rods
20. A permanent magnet 22 is embedded or mounted in the side edge
24 of each belt row 20 at the inside of the turn 15. In some
instances, the magnets need not reside in each row and can be
embedded in every second row, third row, or as needed. The belt
rides along a carryway portion of its conveying path atop
wearstrips or a carryway pan 23 supported in a conveyor frame 26.
The conveyor frame includes an inside rail 28 along the inside of
the turn. Electromagnets 30 are mounted on the inside rail 28. The
electromagnets, when energized, create a magnetic field 32 that
repels the magnets 22 in the inside edge 24 of the belt 12 to
position the conveyor belt radially, or laterally, away from the
inside rail 28. (In the case of a radius belt in a turn,
"laterally" is synonymous with "radially.") In this way, friction
between the side edges 24 of the belt and the inside rail 28
including the electromagnets is eliminated in the turn.
[0014] FIG. 3 shows another version of a conveyor in which the side
edge 34 of a radius conveyor belt 36 is prevented from contacting
an inside rail 38 at the inside of the turn by magnetic repulsive
forces in the outside of the turn. The conveyor belt 36 has a
depending element 40 extending below the bottom surface 42 of the
rest of the belt. Embedded in the depending element are one or more
magnets 43. An electromagnet 44 is mounted in the outer side 46 of
a conveyor pan 48. The electromagnet generates a magnetic field 50
that interacts with the belt magnet 43 to repel the depending
element outward and position the belt laterally, or radially, with
its inside edge 34 away from the inside rail 38. The inside and
outside rails 38, 39 have horizontal lips overlapping the inside
and outside edges 34, 35 of the belt to prevent the belt edges from
rising out of the carryway.
[0015] FIGS. 4A-4D show a conveyor belt 52 that uses magnetic
attractive forces to pull an inside edge 54 of the belt laterally,
or radially, spaced away from an inside rail 56. The belt is
supported in the conveyor frame 26 on wearstrips 23'. The belt
includes magnets 58 in an outer side edge 55 or includes magnetized
or unmagnetized pieces of material that are attracted by
electromagnets 60 in an outside rail 57. Thus, the magnetic
properties for attraction may be provided by magnetized or
unmagnetized ferromagnetic materials. The magnetic force of
attraction pulls the belt laterally, or radially, outward in the
turn in a position out of frictional contact with the inside rail.
Displacement sensors 59 mounted at spaced apart locations along the
length of the outside rail 57 are used to detect the proximity of
the outside edge 55 to the outside rail. FIG. 4E shows one version
of an outside-edge belt module 53 usable in a
modular-plastic-conveyor-belt realization of the belt 52. The
permanent magnets 52 are embedded in the outer side edge 55 of the
module. Proximity sensors, which can be set to detect only one
specific distance, may alternatively be used instead of
displacement sensors, which can measure actual distances.
[0016] FIG. 5 shows a radius conveyor belt 62 with a magnetic hold
down system. The belt has a depending element 64 extending downward
from the bottom side 66 of the belt in a gap 68 between a pair of
carryway support surfaces 70, 71. A magnet 72 embedded in the
depending element in the gap is oriented on an angle relative to
the bottom surface of the belt. An electromagnet 74 mounted in the
outer side of the first support surface at the gap generates a
magnetic field 76 that repels the belt magnet 72 with a downward
component of force F.sub.d that counteracts the tendency of the
radius belt to rise at the outside of the turn. Thus, the magnetic
interaction determines the belt's vertical and lateral, or radial,
position.
[0017] A levitating conveyor 78 is shown in FIGS. 6A-6C. The
conveyor includes a radius belt 80, whose side edges 82, 83 include
magnets 84. Electromagnets 86, 86', 86'' disposed in or near side
rails 88, 89 are controlled to generate magnetic fields that
levitate the belt vertically above an underlying support frame 90,
center the belt laterally away from both the inner and outer side
rails 88, 89, and prevent the belt from rising into contact with
the top lips 92, 93 of the side rails. The relative field strengths
of the electromagnets are modulated to position the belt laterally,
or radially, and vertically. Not all three sets of electromagnets
86, 86', 86'' at each side rail 88, 89 have to be used. For
example, a levitating conveyor can be realized by using the lower
electromagnets 86 to repel the belt upward above the support frame
90 or by using the upper electromagnets 86'' to attract the belt
upward. The side electromagnets 86' may be used as needed to
maintain the lateral, or radial, position of the belt centered
between the vertical surfaces of the opposite side rails with
little or no frictional contact. For greater or more uniform
levitation across the lateral width of the conveyor, additional
electromagnets 87 may be arranged in electromagnet support
structure 85 to interact with additional permanent magnets 84' in
the belt 80. Displacement or proximity sensors 59, mounted in the
electromagnet support structure 85 underlying the belt, detect the
elevation of the belt in the conveyor carryway. Thus, the levitated
belt, which may alternatively be a straight-running belt, can be
operated with low friction. FIG. 6D shows one version of an
outside-edge belt module 91 usable in a
modular-plastic-conveyor-belt realization of the belt 80. The
permanent magnets 84, 84' are embedded in the outer side edge 55
and in bottom-side structure 94 of the module.
[0018] A simplified version of a closed-loop control system for
adjusting the electromagnets for optimal or desired operation of
the belt is illustrated by the block diagram of FIG. 7. A
controller 98, such as a programmable logic controller, work
station, or other programmable computing device, receives an input
signal 100 from a sensor 102 embedded in the belt (see FIG. 2) or
from a sensor 102', such as the displacement sensors of FIG. 4 or 6
or a current sensor measuring motor current in a belt drive motor
116, in the conveyor frame or on one of the belt's drive components
(motor, motor controller, gearbox, or shaft). The sensor or sensors
sense one or more operating conditions of the belt, such as belt
speed, belt tension, belt loading, or belt elevation. A sensor for
belt speed can be realized, for example, as a tachometer mounted to
the drive or idle shaft or as a belt cycle counter mounted to the
conveyor frame counting belt magnets as they pass by. A sensor for
belt tension can be realized as a tension sensor mounted in the
belt or as an optical sensor in the side rails sensing belt
elongation. A sensor for belt loading can be realized as a weight
sensor mounted in the conveyor frame, as a piezoelectric sensor
mounted in the belt, or as a motor current sensor. Belt elevation
can be sensed by optical or proximity sensors mounted in the side
rails. Belt lateral, or radial, position can be sensed by
proximity, displacement, or optical sensors in the side rails or on
the belt. The measurements made by belt-borne sensors 102 are
buffered and transmitted by a transmitter 104 in the belt over an
antenna 106. The transmitted sensor signal is received via a remote
antenna 108 and receiver 110. The receiver sends the sensor signal
to the controller 98. Sensors 102 mounted in the conveyor frame may
send their signals to the controller 98 over a hardwired
connection, as shown by the dashed lines in FIG. 7, or wirelessly
as in the case of belt-borne sensors 102. Control algorithms
running in the controller use the sensor signals, factory or
operator settings, dynamic models of the conveyor belt, and the
magnetic properties of the belts and electromagnets to adjust the
field strength, or amplitude, and, in some cases, the polarities of
the magnetic fields to position the belt to maintain desired or
proper operating conditions. The controller 98 outputs
electromagnet control signals 112 to the electromagnets 114 to
adjust their fields appropriately. For example, an increase in
motor current can indicate a rise in belt tension caused by
increased frictional contact between the belt and the inside
conveyor rail. The controller could respond to the increased motor
current by increasing the repulsive force of the electromagnets to
push the inside edge of the belt away from the rail and reduce
contact and belt tension. The controller can optionally be
programmed to control the speed of the belt's drive motor 116 with
a motor-control signal 118. Drivers (not shown) connected between
the controller and the electromagnets and motor boost the power to
a level sufficient to drive the electromagnets and the motor.
[0019] The various arrangements of magnets and electromagnets
described represent just some of the possible arrangements for
controlling the horizontal or vertical position of a conveyor belt
along a carryway. And although the belts were shown with discrete
permanent magnets or unmagnetized ferromagnetic elements, the
magnetic properties of those elements of the belts can be realized
as well by mixing ferromagnetic materials with polymer materials
and injection molding those together to form a homogeneous
thermoplastic belt module with magnetic properties or by
overmolding an outer thermoplastic belt shell around a
ferromagnetic core or ferromagnetic elements. Furthermore, the
belts may be modular plastic conveyor belts as described, flat
rubber or plastic conveyor belts, metal belts or chains, or
non-metal belts or chains linked by metal hinge rods, as long as a
controllable force can be made to act on them by interaction with
magnetic fields generated by electromagnets.
* * * * *